A. Field of the Invention
The invention relates to the field of computer-based document production, and in particular to a system for receiving, modifying and transmitting documents to output devices.
B. Description of the Related Art
Complex information management systems, such as that described in allowed application Ser. No. 07/446,937, filed contemporaneously herewith and incorporated by reference herein, may operate on several distinct data types. These can include encodings for text, geometric abstracts (graphics), and scanned or bitmapped images. Each data type must be stored, accessed, manipulated and displayed according to rules that differ from those governing the other data types. Furthermore, a number of different representation and encoding formats are available for each data type; these include ASCII and EBCDIC coding for text, ITF units for type, GKS metafile for computer-aided design (CAD) graphics, Group IV CCITT code for scanned lineart, Postscript files (Postscript is produced and sold by Adobe Systems, Inc.), MacDraw files (MacDraw is produced and sold by Apple Computer, Inc.) and Eikonix image formats (produced and sold by Eastman Kodak Company), among others. Text can reside in system memory along with compositional attributes (e.g. typeface, size, position, color) embedded therein, or as generic (e.g. pure ASCII or EBCDIC) character strings. The divergent generic rules and specific formats relating to encoded data present significant input/output difficulties.
Document production systems typically contain (or, in the case of simple word processing systems, are built around) editing functions that allow the user to add, modify or delete text prior to final output. An editing facility (often referred to as an "application program" due to the multiplicity of possible editing tasks) must accept user input and operate on the particular data type(s) and encoding format(s) for which it is configured. Often, users of current document management systems sequentially call a series of appropriate editors to modify a particular block of data.
After input and editing have been completed, the data representing a document is sent to one or more output devices, such as a printer, image setter, or the interactive terminal on which editing takes place. Output devices differ in display mode, resolution, functionality, command syntax, data encoding and other operational constraints. Current document management systems must be tailored to the particular output devices employed, or external output software modules purchased and installed.